Histopathological assessment of tissues. Histopathologic assessments of hematoxylin and eosin–stained slides were conducted by a veterinary pathologist. Representative images of tissues and lesions of lymphocytic infiltration were captured at the indicated magnifications for the main and inset images. The evaluation results, including the morphologic diagnoses of the organs and the summaries of the mean scores, are provided in supplemental Table 3. Liver and spleen: n = 8/no disease, n = 8/EV, n = 8/BTK^WT, n = 9/BTK^C481S, and n = 9/BTK^C481R. Bone: n = 8/no disease, n = 6/EV, n = 7/BTK^WT, n = 6/BTK^C481S, and n = 6/BTK^C481R.